Studying fall bird migration

ByScott Shalaway

The fall bird migration actually begins in July. Along East Coast beaches, shorebirds that nested in the Arctic begin showing up along coastlines in mid-July. August arctic snowstorms happen, so arctic migrants fledge their young as quickly as possible to get an early start south.

Closer to home, male ruby-throated hummingbirds begin heading south in early August. Any hummers you see right now are probably migrants from farther north. Depending on the species, the fall bird migration runs from July through November (golden eagles).

The most impressive migrants are long-distance travelers. Arctic terns, for example, make a 22,000-mile round trip to and from the tip of the Americas. But advances in tracking technology have revealed other long-distance wanderers.

Sooty shearwaters, for example, roam the Pacific Ocean most of the year. One population follows a figure-eight pattern that takes them from Antarctica to the Bering Sea. Though they nest in the south Pacific, these long journeys keep the birds in areas where food is abundant.

We know about these phenomenal movements thanks to tiny geolocaters attached to captured birds. When the birds are recaptured, the data recorded by the geolocator can be downloaded and analyzed by computer.

Geolocators record a variety of information including the amount of daylight, which is used to determine latitude and longitude on a daily basis so their movements can be determined. Some units also record air and water temperature and even depths to which birds dive to feed.

Geolocator tags are used to monitor movements of everything from whales and sea turtles to fish and seals. Some units are so small they can be used to track small songbirds and even invertebrates.

Despite their virtues, geolocators have not made electronic transmitters obsolete. Satellite transmitters enabled biologists in Ohio to track migrating ospreys to their wintering grounds in the Amazon basin. And more recently biologists at the Center for Conservation Biology in Williamsburg, Virginia have made some stunning discoveries about the migration of whimbrels, a large shorebird with a long, decurved bill.

Whimbrels nest in northern Alaska and Canada and winter on the northern coast of South America. By attaching tiny satellite transmitters to 19 individuals over the last three years, biologists have discovered an unlikely migratory path.

Birds that nest in northern Alaska fly across the continent to the northeast coast and then out over the Atlantic Ocean. Then they turn south and stop along the Delmarva Peninsula to refuel.

After a few weeks, they continue south through the Atlantic en route to the coast of South America. Along the way, they stop at Caribbean islands to rest and feed. Fletcher Smith, biologist in charge of the project says the distances these birds travel are, "simply staggering. However, their jaw-dropping feats involving storms are even more amazing."

In 2011, for example, a whimbrel named Hope, flew into a large tropical storm off the eastern shore of Canada. For 27 hours she flew nonstop, averaging just nine miles per hour to reach the center of the storm. On the backside of the storm, tailwinds grabbed her and she flew 92 mph for an hour-and-a-half to exit the storm. This is clearly an important way some migratory birds get through huge tropical storms during migration.

Unfortunately, if whimbrels make it to the Caribbean Islands en route to South America, they are often greeted by unregulated hunters. Several transmitter-equipped birds have been lost to wing shooters on these islands.

Learning about the migratory path of whimbrels highlights the importance of international cooperation to protect migratory birds. George Fenwick, president of the American Bird Conservancy (www.abcbirds.org) says, "These shooting parties are the antithesis of everything the hunting community stands for here in the U.S. They give nothing back in the way of permit fees to promote conservation efforts and sometimes don't even bother to collect the birds they shoot."

Fenwick hopes that, "Sometimes something good comes from something bad, and in this case, I believe the good that may emerge is that island conservation groups and regulators will begin to take a more critical view of how to more effectively manage hunting practices in their communities."